3.19.8-ckt5 -stable review patch. If anyone has any objections, please let me know.
------------------ From: "Kirill A. Shutemov" <[email protected]> commit 6b7339f4c31ad69c8e9c0b2859276e22cf72176d upstream. Reading page fault handler code I've noticed that under right circumstances kernel would map anonymous pages into file mappings: if the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated on ->mmap(), kernel would handle page fault to not populated pte with do_anonymous_page(). Let's change page fault handler to use do_anonymous_page() only on anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not shared. For file mappings without vm_ops->fault() or shred VMA without vm_ops, page fault on pte_none() entry would lead to SIGBUS. Signed-off-by: Kirill A. Shutemov <[email protected]> Acked-by: Oleg Nesterov <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Willy Tarreau <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> [ kamal: backport to 3.19-stable: s/do_fault/do_linear_fault/ ] Signed-off-by: Kamal Mostafa <[email protected]> --- mm/memory.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 6aa7822..f5d0e3d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2630,6 +2630,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap(page_table); + /* File mapping without ->vm_ops ? */ + if (vma->vm_flags & VM_SHARED) + return VM_FAULT_SIGBUS; + /* Check if we need to add a guard page to the stack */ if (check_stack_guard_page(vma, address) < 0) return VM_FAULT_SIGSEGV; @@ -3040,6 +3044,9 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma, - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; pte_unmap(page_table); + /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ + if (!vma->vm_ops->fault) + return VM_FAULT_SIGBUS; if (!(flags & FAULT_FLAG_WRITE)) return do_read_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); @@ -3214,13 +3221,12 @@ static int handle_pte_fault(struct mm_struct *mm, barrier(); if (!pte_present(entry)) { if (pte_none(entry)) { - if (vma->vm_ops) { - if (likely(vma->vm_ops->fault)) - return do_linear_fault(mm, vma, address, - pte, pmd, flags, entry); - } - return do_anonymous_page(mm, vma, address, - pte, pmd, flags); + if (vma->vm_ops) + return do_linear_fault(mm, vma, address, pte, + pmd, flags, entry); + + return do_anonymous_page(mm, vma, address, pte, pmd, + flags); } if (pte_file(entry)) return do_nonlinear_fault(mm, vma, address, -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
